Since the first flight of the Boeing 737-100 in April 1967 more than 6,000 examples of this hugely successful short-medium-range aircraft have been ordered, making it easily the best selling commercial airliner in history.

Today, the Boeing 737 represents more than 25% of the worldwide fleet of large commercial jet airliners.

Three main versions have been produced, the Boeing 737-100/-200, powered by Pratt & Whitney JT8D engines, the Boeing 737-300/-400/-500, introducing high bypass ratio CFM56 turbofans and more advanced avionics, and the Next Generation Boeing 737-600/-700/-800, delivered to the first customer in December 1997.

This achieved a record 1,500 deliveries within six years. Next Generation Boeing 737s feature more efficient CFM56 engines, a new wing, larger fin and all-new flight deck.

The Boeing 737 has been sold to more than 540 airlines and on average there are 1,250 in the air at any one time. Boeing has also developed a 737 business jet version called the Boeing Business Jet and in January announced development of the extended range Boeing 737-700ER.

It is currently considering replacement types under its Boeing 737 Replacement Study, which is looking into potential aircraft in the 100-seat and 150-seat categories.

Faced with fast-growing competition in the short-haul jet market in the late 1950s and early 1960s, Boeing began design of the 737 in November 1964.

Aimed initially at a requirement for an 85-seater with a 925km range and good short-field capability, the first Boeing 737 concepts closely resembled the T-tail designs of existing short/medium -range aircraft such as the British Aircraft Corporation One-Eleven and Douglas DC-9.

The Boeing 737 underwing engine location was chosen by legendary Boeing designer Jack Steiner, who also decided to base the Boeing 737 design on the same fuselage section as the successful Boeing 707 and Boeing 727.

The Boeing 737 was finally launched in 1965 with an order for 22 aircraft from Lufthansa, but the programme was then almost cancelled and sold off to Japan for lack of funds. Another low point occurred during the oil crisis of the early 1970s, when orders slumped.

The first major development of the Boeing 737 came in November 1981 with launch of the re-engined Boeing 737-300 with orders from Southwest Airlines and USAir. The 126-seat Next Generation 737-700 was launched in November 1993 and was followed by the 737-800 in 1994, the 737–600 in 1995 and the 737–900 in 1999.